1. Field of the Invention
Embodiments of the invention relate to a stereoscopic image display and a method for driving the same.
2. Discussion of the Related Art
A stereoscopic image display implements a three-dimensional (3D) image using a stereoscopic technique or an autostereoscopic technique. The stereoscopic technique, which uses a parallax image between left and right eyes of a user with a high stereoscopic effect, may include a glasses type method and a non-glasses type method. In the glasses type method, a stereoscopic image is implemented on a direct-view display or a projector using polarization glasses by varying a polarization direction of the parallax image between the left and right eyes. Alternatively, the stereoscopic image is implemented on the direct-view display or the projector using liquid crystal shutter glasses by displaying the parallax image between the left and right eyes in a time-division manner. In the non-glasses type method, an optical part such as a parallax barrier and a lenticular lens for separating an optical axis of the parallax image between the left and right eyes is generally installed in front of or behind a display screen, and thus the stereoscopic image is implemented.
FIG. 1 illustrates a related art patterned retarder type stereoscopic image display. As shown in FIG. 1, the patterned retarder type stereoscopic image display implements a 3D image using polarization characteristic of a patterned retarder 5 disposed on a display panel 3 and polarization characteristic of polarization glasses 6 a user wears. The patterned retarder type stereoscopic image display displays a left eye image L and a right eye image R on adjacent lines of the display panel 3 and switches polarization characteristics of light incident on the polarization glasses 6 through the patterned retarder 5. The patterned retarder type stereoscopic image display allows polarization characteristic of the left eye image L to be different from polarization characteristic of the right eye image R and spatially divides the left eye image L and the right eye image R the user sees, thereby implementing the 3D image. In FIG. 1, a reference numeral 1 denotes a backlight unit providing light to the display panel 3, and reference numerals 2 and 4 denote polarizing films, that are respectively attached to an upper substrate and a lower substrate of the display panel 3 so as to select linear polarization.
In the patterned retarder type stereoscopic image display shown in FIG. 1, visibility of the 3D image is degraded because of a crosstalk generated at a position of a vertical viewing angle. The user's left eye has to transmit only light of the left eye image L and the user's right eye has to transmit only light of the right eye image R, so that the user can sufficiently feel a stereoscopic feeling of the 3D image. However, when both the light of the left eye image L and the light of the right eye image R are incident on the user's left and right eyes, the user sees both the light of the left eye image L and the light of the right eye image R through the user's left or right eye, thereby perceiving the crosstalk. When the user does not view the 3D image in the front of the display panel 3 and looks down or up the 3D image, the crosstalk is generated at the vertical viewing angle, that is equal to or greater than a predetermined angle. Thus, the related art patterned retarder type stereoscopic image display has the very narrow vertical viewing angle at which the user can view the 3D image without the crosstalk.
Thus, as shown in FIG. 2, Japanese Laid Open Publication No. 2002-185983 discloses a method for widening an vertical viewing angle of a stereoscopic image display by forming black stripes BS in a patterned retarder 5. When the user observes the stereoscopic image display at a location spaced apart from the stereoscopic image display by a predetermined distance D, an vertical viewing angle α, at which the crosstalk is not theoretically generated, depends on the size of black matrixes BM of a display panel 3, the size of the black stripes BS of the patterned retarder 5, and a distance S between the display panel 3 and the patterned retarder 5. The vertical viewing angle a widens as the size of the black matrixes BM and the size of the black stripes BS increase and as the distance S between the display panel 3 and the patterned retarder 5 decreases.
However, a luminance of the stereoscopic image display including the black stripes BS formed in the patterned retarder 5 is much less than a luminance of the existing display device displaying only a two-dimensional (2D) image because of the black stripes BS. Further, the stereoscopic image display including the black stripes BS formed in the patterned retarder 5 requires the precision alignment when the patterned retarder 5 is attached to the display panel 3. When the patterned retarder 5 is not accurately aligned, operations of the black stripes BS are not smoothly performed. Therefore, the user may view the left eye image through his/her right eye or may view the right eye image through his/her left eye. As a result, the user may perceive the crosstalk. Thus, a technology for controlling pixels of the display panel using active black stripes has been proposed, so as to solve the problems of the stereoscopic image display disclosed in Japanese Laid Open Publication No. 2002-185983.